Johannes Lang

Transnasal Approach to the Pituitary Region

In our material (Lang and Schafer 1976) there are two to six small arteries arising from the cavernous part of the internal carotid artery. Most commonly there are two main trunks which we term the posterior and lateral caroticocavernous trunks. The posterior caroticocavernous trunk branches off in the vicinity of the posterior sinus curve of the internal carotid artery. It is approximately 1 mm in width and runs at first dorsally for 2–7 mm inside the cavernous sinus, then dividing into two or three branches. The posterior inferior hypophyseal artery usually runs medially and forwards. This vessel usually pursues a tortuous course between the internal carotid artery and the dorsum sellae, running medially to the basal part of the posterior pituitary lobe, where it frequently divides into two branches which embrace the posterior lobe. A ramus superior runs on the upper posterior part of the posterior lobe, and a ramus inferior on the lower posterior part (Fig. 131).

Midbrain and Adjacent Structures

The mesencephalon connects those parts of the brain in the hypophyseal region (diencephalon) with those in the posterior cranial fossa (rhombencephalon).

Floor and Contents of the Middle Cranial Fossa

The bony floor of the middle cranial fossa is bounded rostrally by the posterior border of the lesser wing of the sphenoid and its lateral extension, which we term the crista alaris (Sylvii). Below this bony ridge the greater wing of the sphenoid forms a hollow for the pole of the temporal lobe. This hollow extends forwards for a variable distance. Further posteriorly, the basal gyri of the temporal lobe lie against the floor of the temporal fossa. In its medial part the greater wing extends further dorsally than in its lateral part, and the squamous temporal bone makes up much of the floor and lateral wall of the middle fossa. The dorsal boundary of the bony floor of the middle cranial fossa is formed by the anterior surface of the petrous part of the temporal bone. The floor of the middle fossa carries a number of portals for the passage of cranial nerves and vessels.

Cavernous Sinus and Trigeminal Ganglion

In 1975 we pointed out that the lateral wall of the right cavernous sinus is usually closer to the vertical plane than the corresponding wall of the left cavernous sinus (Lang 1975). Furthermore, the foramina rotundum and ovale on the right side lie closer to the median plane than on the left. At the level of the diaphragmatic foramen the lateral wall of the right cavernous sinus forms an angle of 98o with a tangent passing through the upper margin of the anterior petroclinoid fold, while the corresponding angle on the left is 110° (for details see Diagram 72). In the vicinity of the cavernous sinus the lateral and anterior walls, and in part the upper wall, of the cavum trigeminale (and also certain areas lying rostral to the latter) are known as dura propria (Hollinshead 1968). We designated the lateral wall as the sagittal plate of the cavernous sinus. It is formed from the dura mater of the middle cranial fossa and can be separated into two layers, a superficial layer (adjacent to the brain) and a deep layer. After dissecting off the superficial layer (lamina propria) the ophthalmic, maxillary and trochlear nerves come into view together with the oculomotor nerve and the outer wall of the cavum trigeminale. The lateral and upper walls of the cavum trigeminale are fused with the trigeminal ganglion in the area of the middle cranial fossa. In our dissections (52 half heads) the average distance between the upper border of the trigeminal ganglion and the lateral wall of the skull was 41.0 (30.0–48.5) mm on the right, and 40.1 (32.5–54.0) mm on the left.

Anterior Cranial Fossa, the Approach to the Orbit and the Ethmoid Bone

The thinnest part of the floor of the anterior cranial fossa is in the roof of the orbit; during postnatal development it moves from the anteromedial to the posterolateral part (Lang and Bruckner 1981). 21. The thinnest zones of the floor of the anterior cranial fossa average 0.2 mm in the newborn and increase in thickness with age, though very inconsistently, reaching 0.66–1.13 mm at 17 years of age.

Cisternae and Vessels of the Pituitary and Diencephalon

The spaces within which the cerebrospinal fluid circulates are bounded on the brain side by the pia mater and on the external side by the arachnoid. The pia mater consists essentially of collagen fibers and is everywhere closely apposed to the brain surface. In certain regions this layer of fibers is particularly thick (medulla oblongata, pons, optic nerves, chiasma, etc.). In other zones it is usually thinner (superolateral, medial and inferior surfaces of the hemispheres).

The Floor of the Orbit

The orbital floor slopes forwards and downwards in relation to the Frankfurt horizontal plane and its major part is made up of the orbital surface of the maxilla. Just before it reaches the inferior orbital margin the floor usually turns upwards again for a short distance. The anterolateral portion of the orbital floor consists of the zygomatic bone, which also forms the lateral part of the infraorbital margin and extends dorsally as far as the anterior end of the inferior orbital fissure. The nasolacrimal canal leads from the anteromedial corner of the orbital floor into the nasal cavity. The extreme posterior part of the floor is formed by the orbital lamina of the palatine bone, a structure which varies in size. Posterolaterally, the floor is bounded by the inferior orbital fissure while anterolaterally it curves upwards into the lateral wall of the orbit. The medial region of the floor is somewhat elevated and merges smoothly into the medial wall of the orbit.

Pituitary Region and Anterior Cranial Fossa: Approaches via the Cranium

The muscle arises from the roughly semicircular planum temporale, situated below the inferior temporal line, and from the region of the temporal fossa. Together with its superficial part, which also arises from the deep lamina of the temporal fascia, it makes up in adults approximately 37.5% of the total mass of the muscles of mastication on each side. Its physiological cross-section amounts to approximately 4.1 cm2. For further details see Lanz/Wachs- Muth, Praktische Anatomie, Vol. I, 1C.

Diploic Veins, Meninges and Scalp

The frontal, anterior temporal, posterior temporal and occipital diploic veins all exhibit individual variations. Right-left differences are nearly always present. The diploic veins traverse the sutures and they may drain into the venous sinuses of the dura mater (occipital, frontal and posterior temporal diploic veins) or into veins accompanying the frontal branch of the middle meningeal artery (anterior temporal diploic vein). Communications with the emissary veins (parietal, mastoid and occipital) have also been observed.

Skull: Data for Computed Tomography

Schwalbe (1902) and Nagel (1904) determined the angles between these planes. Nagel found the mean angle between the glabella-inion plane and the Frankfurt plane in Europeans to be 15°. It was 15.4 (10–21)° in Bavarian men and 15.1 (12–19)o in Bavarian women. Schwalbe studied inhabitants of Alsace and obtained values of 16.2 (10–21)° in men and 16.1 (12–20)° in women. The mean angle found in other Europeans by Nagel was 13.5 (9–21)°.